The subject matter disclosed herein generally relates to graphite fibers joined to a substrate material. More particularly, the subject matter disclosed herein relates to graphite fiber and substrate structures for heat exchanger systems.
Graphite fiber material, for example, Fibercore®, is often utilized in heat exchange applications. The material comprises an array of graphite fibers having voids between adjacent fibers. In such applications, voids in the material may be filled with a heat storage, or phase change, material such as wax, water or the like. In some applications, no heat storage material is added. Large pieces of the graphite fiber material are typically bonded to a desired surface, for example, an aluminum component, via an adhesive. Thermal mismatch issues are common between bulk graphite and graphite foam when joined to a metallic substrate. For example, graphite materials typically have a coefficient of thermal expansion in the range of about 0-2 μin/in/° F., while for metals this coefficient is in the range of about 5-12 μin/in/° F. and for polymers the coefficient is in the range of about 10-70 μin/in/° F. The graphite fiber material is not a monolithic structure and as such accommodates the thermal mismatch by translating with the substrate during thermal processing. Further, the thickness of the graphite fiber material layer, which is relative to a length of the graphite fibers in the material, is limited due to capability of graphite fiber production. The relatively thin graphite fiber material is fragile and is subject to breakage and damage when handling and/or shaping by machining or the like into desired shapes. The art would well receive a more robust structure of graphite fiber material, which is not as sensitive to handling and/or other processing and which improves the thermal mismatch issues that exist in current structures. Also, in this process, a multilayered graphite fiber material structure may be obtained.